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2002


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Critical magnetic properties of disordered polycrystalline Cr75Fe25 and Cr70Fe30 alloys

Fischer, S. F., Kaul, S. N., Kronmüller, H.

{Physical Review B}, 65(6), 2002 (article)

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[BibTex]

2002


[BibTex]


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Magnetic properties of ion-beam sputtered Cr3Fe-alloy films

Fischer, S. F., Kaul, S. N., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 240(1-3):374-376, 2002 (article)

mms

[BibTex]

[BibTex]


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Model-independent measurements of hydrogen diffusivity in the yttrium dihydrides

Majer, G., Gottwald, J., Peterson, D. T., Barnes, R. G.

{Journal of Alloys and Compounds}, 330-332, pages: 438-442, 2002 (article)

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[BibTex]

[BibTex]


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Strong anisotropy of projected Cr3d moments of epitaxial grown CrO2-films

Goering, E., Bayer, A., Gold, S., Schütz, G.

{Bessy-Highlights}, pages: 26-27, 2002 (article)

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[BibTex]

[BibTex]


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Change from a bulk discontinuous phase transition in V2H to a contiuous transition in a defective near-surface skin layer

Trenkler, J., Abe, H., Wochner, P., Haeffner, D., Bail, J., Carstanjen, H. D., Moss, S.

{Modelling and Simulation in Materials Science and Engineering}, 8, pages: 269-275, 2002 (article)

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[BibTex]

[BibTex]


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Evidence for van der Waals adhesion in gecko setae

Autumn, K., Sitti, M., Liang, Y. A., Peattie, A. M., Hansen, W. R., Sponberg, S., Kenny, T. W., Fearing, R., Israelachvili, J. N., Full, R. J.

Proceedings of the National Academy of Sciences, 99(19):12252-12256, National Acad Sciences, 2002 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


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Vacancies in thermal equilibrium and ferromagnetism near the Curie temperature

Seeger, A., Fähnle, M.

{Zeitschrift f\"ur Metallkunde}, 93(10):1030-1042, 2002 (article)

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[BibTex]

[BibTex]


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Magnetic imaging with soft X-ray microscopy

Fischer, P., Denbeaux, G., Eimüller, T., Goll, D., Schütz, G.

{IEEE Transactions on Magnetics}, 38(5):2427-2431, 2002 (article)

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[BibTex]

[BibTex]


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Theory of induced magnetic moments and x-ray magnetic circular dichroism in Co-Pt multilayers

Ederer, C., Komelj, M., Fähnle, M., Schütz, G.

{Physical Review B}, 66(9), 2002 (article)

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[BibTex]

[BibTex]


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Determination of the complete set of second-order magnetoelastic coupling constants on epitaxial films

Komelj, M., Fähnle, M.

{Physical Review B}, 65(21), 2002 (article)

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[BibTex]

[BibTex]


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Undulation instabilities in laterally structured magnetic multilayers

Eimüller, T., Scholz, M., Guttmann, P., Köhler, M., Bayreuther, G., Schmahl, G., Fischer, P., Schütz, G.

{Journal of Applied Physics}, 91(10):7334-7336, 2002 (article)

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[BibTex]

[BibTex]


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Initial oxidation of AlPdMn quasicrystals - A study by high-resolution RBS and ERDA

Plachke, D., Khellaf, A., Carstanjen, H. D.

{Nuclear Instruments \& Methods in Physics Research B}, 190, pages: 646-651, 2002 (article)

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[BibTex]

[BibTex]


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The Verwey transition - a topical review

Walz, F.

{Journal of Physics-Condensed Matter}, 14(12):R285-R340, 2002 (article)

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[BibTex]

[BibTex]


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Composition dependence of the Zener relaxation in high-purity FeCr single crystals

Hirscher, M., Ege, M.

{Materials \textquotesingleTransactions JIM}, 43(2):182-185, 2002 (article)

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[BibTex]

[BibTex]


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Hydrogen storage in carbon nanostructures

Hirscher, M., Becher, M., Haluska, M., Quintel, A., Skakalova, V., Choi, Y. M., Dettlaff-Weglikowska, U., Roth, S., Stepanek, I., Bernier, P., Leonhardt, A., Fink, J.

{Journal of Alloys and Compounds}, 330, pages: 654-658, 2002 (article)

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[BibTex]

[BibTex]


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Micromagnetic investigation of sub-100-nm magnetic domains in atomically stacked Fe(001)/Au(001) multilayers

Köhler, M., Zweck, J., Bayreuther, G., Fischer, P., Schütz, G., Denbeaux, G., Attwood, D.

{Journal of Magnetism and Magnetic Materials}, 240, pages: 79-82, 2002 (article)

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DOI [BibTex]

DOI [BibTex]


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Experimental Study of a Crystal Positron Source

Chehab, R., Cizeron, R., Sylvia, C., Baier, V., Beloborodov, K., Bukin, A., Burdin, S., Dimova, T., Drozdetsky, A., Druzhinin, V., Dubrovin, M., Golubev, V., Serednyakov, S., Shary, V., Strakhovenko, V., Artru, X., Chevallier, M., Dauvergne, D., Kirsch, R., Lautesse, P., Poizat, J. C., Remillieux, J., Jejcic, A., Keppler, P., Major, J., Gatignon, L., Bochek, G., Kulibaba, V., Maslov, N., Bogdanov, A., Potylitsin, A., Vnukov, I.

{Physics Letters B}, 525, pages: 41-48, 2002 (article)

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[BibTex]

[BibTex]

2001


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Regularized principal manifolds

Smola, A., Mika, S., Schölkopf, B., Williamson, R.

Journal of Machine Learning Research, 1, pages: 179-209, June 2001 (article)

Abstract
Many settings of unsupervised learning can be viewed as quantization problems - the minimization of the expected quantization error subject to some restrictions. This allows the use of tools such as regularization from the theory of (supervised) risk minimization for unsupervised learning. This setting turns out to be closely related to principal curves, the generative topographic map, and robust coding. We explore this connection in two ways: (1) we propose an algorithm for finding principal manifolds that can be regularized in a variety of ways; and (2) we derive uniform convergence bounds and hence bounds on the learning rates of the algorithm. In particular, we give bounds on the covering numbers which allows us to obtain nearly optimal learning rates for certain types of regularization operators. Experimental results demonstrate the feasibility of the approach.

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PDF [BibTex]

2001


PDF [BibTex]


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The psychometric function: II. Bootstrap-based confidence intervals and sampling

Wichmann, F., Hill, N.

Perception and Psychophysics, 63 (8), pages: 1314-1329, 2001 (article)

ei

PDF [BibTex]

PDF [BibTex]


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The psychometric function: I. Fitting, sampling and goodness-of-fit

Wichmann, F., Hill, N.

Perception and Psychophysics, 63 (8), pages: 1293-1313, 2001 (article)

Abstract
The psychometric function relates an observer'sperformance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function'sparameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (or lapses ). We show that failure to account for this can lead to serious biases in estimates of the psychometric function'sparameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditional X^2 methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods

ei

PDF [BibTex]

PDF [BibTex]


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Markovian domain fingerprinting: statistical segmentation of protein sequences

Bejerano, G., Seldin, Y., Margalit, H., Tishby, N.

Bioinformatics, 17(10):927-934, 2001 (article)

ei

PDF Web [BibTex]

PDF Web [BibTex]


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Isotropic second-order nonlinear optical susceptibilities

Fischer, P., Buckingham, A., Albrecht, A.

PHYSICAL REVIEW A, 64(5), 2001 (article)

Abstract
The second-order nonlinear optical susceptibility, in the electric dipole approximation, is only nonvanishing for materials that are noncentrosymmetric. Should the medium be isotropic, then only a chiral system. such as an optically active liquid, satisfies this symmetry requirement. We derive the quantum-mechanical form of the isotropic component of the sum- and difference-frequency susceptibility and discuss its unusual spectral properties. We show that any coherent second-order nonlinear optical process in a system of randomly oriented molecules requires the medium to be chiral. and the incident frequencies to be different and nonzero. Furthermore, a minimum of two nondegenerate excited molecular states are needed for the isotropic part of the susceptibility to be nonvanishing. The rotationally invariant susceptibility is zero in the static field limit and shows exceptionally sensitive resonance and dephasing effects that are particular to chiral centers.

pf

DOI [BibTex]

DOI [BibTex]


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Reply to “Comment on ‘Phenomenological damping in optical response tensors’”

Buckingham, A., Fischer, P.

PHYSICAL REVIEW A, 63(4), 2001 (article)

Abstract
We show that damping factors must not be incorporated in the perturbation of the ground state by a static electric field. If they are included, as in the theory of Stedman et al. {[}preceding Comment. Phys. Rev. A 63, 047801 (2001)], then there would be an electric dipole in the y direction induced in a hydrogen atom in the M-s = + 1/2 state by a static electric field in the x direction. Such a dipole is excluded by symmetry.

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DOI [BibTex]


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The coercivity of the melt-spun Sm-Fe-Ga-C permanent magnets and the effect of additives (Nb, Cu and Zr)

Zhang, J. X., Kleinschroth, I., Goll, D., Cuevas, F., Kronmüller, H.

{Journal of Physics-Condensed Matter}, 13(46):10487-10496, 2001 (article)

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[BibTex]

[BibTex]


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Hardness-depth profile of a carbon-implanted Ti-6Al-4V alloy and its relation to composition and microstructure

Kunert, M., Kienzle, O., Baretzky, B., Baker, S. P., Mittemeijer, E. J.

{Journal of Materials Research}, 16(8):2321-2335, 2001 (article)

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[BibTex]

[BibTex]


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New Sm(Co, Fe, Cu, Zr)(z) magnets with better temperature stability

Tang, W., Zhang, Y., Goll, D., Hadjipanayis, G. C., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 226(Sp. Iss. SI):1365-1366, 2001 (article)

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[BibTex]

[BibTex]


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Hydrogen in nanostructured vanadium-hydrogen systems

Orimo, S., Kimmerle, F., Majer, G.

{Physical Review B}, 63(9), 2001 (article)

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[BibTex]

[BibTex]


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Diffusion of hydrogen in heterogeneous systems

Herrmann, A., Schimmele, L., Mössinger, J., Hirscher, M., Kronmüller, H.

{Applied Physics A-Materials Science \& Processing}, 72(2):197-208, 2001 (article)

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[BibTex]

[BibTex]


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Structural vacancies in B2-CoAl and NiAl

Meyer, B., Bester, G., Fähnle, M.

{Scripta Materialia}, 44, pages: 2485-2488, 2001 (article)

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[BibTex]

[BibTex]


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Grain boundary phase transition in the Cu-Bi system

Straumal, B. B., Prokofyev, S. I., Chang, L.-S., Sluchanko, N. E., Baretzky, B., Gust, W., Mittemeijer, E. J.

{Diffusion and Defect Forum}, 194-199, pages: 1343-1348, 2001 (article)

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[BibTex]

[BibTex]


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Carbon nanostructures: an efficient hydrogen storage medium for fuel cells

Atkinson, K., Roth, S., Hirscher, M., Grünwald, W.

{Fuel Cells Bulletin}, 4(38):9-12, 2001 (article)

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[BibTex]

[BibTex]


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Magnetic domains in nanostructured media studied with M-TXM

Fischer, P., Eimüller, T., Schütz, G., Bayreuther, G., Tsunashima, S., Tagaki, N., Denbeaux, G., Attwood, D.

{Journal of Synchrotron Radiation}, 8, pages: 325-327, 2001 (article)

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[BibTex]

[BibTex]


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Compound formation and abrasion resistance of ion-implanted Ti6Al4V

Schmidt, H., Schminke, A., Schmiedgen, M., Baretzky, B.

{Acta Materialia}, 49, pages: 487-495, 2001 (article)

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[BibTex]

[BibTex]


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Interpretation of ab initio total energy results in a chemical language: I. Formalism and implementation into a mixed-basis pseudopotential code

Bester, G., Fähnle, M.

{Journal of Physics-Condensed Matter}, 13(50):11541-11550, 2001 (article)

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[BibTex]

[BibTex]


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Faceting of \sum3 and \sum9 grain boundaries in copper

Straumal, B. B., Polyakov, S. A., Bischoff, E., Gust, W., Mittemeijer, E. J.

{Interface Science}, 9(3-4):287-292, 2001 (article)

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[BibTex]

[BibTex]


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Generation and application of ultra-high-intensity magnetic field gradient pulses for NMR spectroscopy

Galvosas, P., Stallmach, F., Seiffert, G., Karger, J., Kaess, U., Majer, G.

{Journal of Magnetic Resonance}, 151(2):260-268, 2001 (article)

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[BibTex]

[BibTex]


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Formation and structure of highly over-stoichiometric LaNi5+x (x\textasciitilde1) alloys obtained by manifold non-equilibrium methods

Cuevas, F., Latroche, M., Hirscher, M., Percheron-Guegan, A.

{Journal of Alloys and Compounds}, 323, pages: 4-7, 2001 (article)

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[BibTex]

[BibTex]


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Hydrogen permeability measurement through Pd, Ni and Fe membranes

Yamakawa, K., Ege, M., Ludescher, B., Hirscher, M., Kronmüller, H.

{Journal of Alloys and Compounds}, 321(1):17-23, 2001 (article)

mms

[BibTex]

[BibTex]


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Ab-initio statistical mechanics for the phase diagram of NiAl including the effect of vacancies

Lechermann, F., Fähnle, M.

{Physica Status Solidi B-Basic Research}, 224(2):R4-R6, 2001 (article)

mms

[BibTex]

[BibTex]


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Uniaxial orientational order-disorder transitions in diammine magnesium halides, Mg(ND3)2Cl2 and Mg(ND3)2Br2, investigated by neutron diffraction

Leineweber, A., Jacobs, H., Fischer, P., Böttger, G.

{Journal of Solid State Chemistry}, 156(2):487-499, 2001 (article)

mms

[BibTex]

[BibTex]


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XMCD study of the Ruddlesden-Popper Phase La1.2Nd0.2Sr1.6Mn2O7

Weigand, F., Goering, E., Geissler, J., Justen, M., Dörr, K., Ruck, K., Schütz, G.

{Journal of Synchrotron Radiation}, 8, pages: 431-433, 2001 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Nonlinear magnetoelastic effect in ultrathin epitaxial fcc Co (001) films: an ab-initio study

Komelj, M., Fähnle, M.

{Journal of Magnetism and Magnetic Materials}, 224, pages: L1-L4, 2001 (article)

mms

[BibTex]

[BibTex]


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Element-specific imaging of magnetic domains at 25 nm spatial Resolution using soft X-ray microscopy

Fischer, P., Eimüller, T., Schütz, G., Denbeaux, G., Pearson, A., Johnson, L., Attwood, D., Tsunashima, S., Kumazawa, M., Takagi, N., Köhler, M., Bayreuther, G.

{Review of Scientific Instruments}, 72, pages: 2322-2324, 2001 (article)

mms

[BibTex]

[BibTex]


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Magnetization reversal of a multilayered FeGd dot array imaged by transmission X-ray microscopy

Eimüller, T., Scholz, M., Guttmann, P., Fischer, P., Köhler, M., Bayreuther, G., Schmahl, G., Schütz, G.

{Journal of Applied Physics}, 89, pages: 7162-7164, 2001 (article)

mms

[BibTex]

[BibTex]


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Ho-Fe - Garnet soft XMCD measurements below and above the compensation temperature

Goering, E., Gold, S., Schütz, G.

{Journal of Synchrotron Radiation}, 8, pages: 422-424, 2001 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Grain boundary grooving as an indicator of grain boundary phase transformations

Schölhammer, J., Baretzky, B., Gust, W., Mittemeijer, E., Straumal, B.

{Interface Science}, 9(1-2):43-53, 2001 (article)

mms

[BibTex]

[BibTex]


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X-MCD study of mixed valence manganites

Sikora, M., Kapusta, C., Zajac, D., Tokarz, W., Attenkofer, K., Fischer, P., Goering, E., Schütz, G.

{Journal of Alloys and Compounds}, 328(1-2):100-104, 2001 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Synchronized robot drumming by neural oscillator

Kotosaka, S., Schaal, S.

Journal of the Robotics Society of Japan, 19(1):116-123, 2001, clmc (article)

Abstract
Sensory-motor integration is one of the key issues in robotics. In this paper, we propose an approach to rhythmic arm movement control that is synchronized with an external signal based on exploiting a simple neural oscillator network. Trajectory generation by the neural oscillator is a biologically inspired method that can allow us to generate a smooth and continuous trajectory. The parameter tuning of the oscillators is used to generate a synchronized movement with wide intervals. We adopted the method for the drumming task as an example task. By using this method, the robot can realize synchronized drumming with wide drumming intervals in real time. The paper also shows the experimental results of drumming by a humanoid robot.

am

[BibTex]

[BibTex]


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Origins and violations of the 2/3 power law in rhythmic 3D movements

Schaal, S., Sternad, D.

Experimental Brain Research, 136, pages: 60-72, 2001, clmc (article)

Abstract
The 2/3 power law, the nonlinear relationship between tangential velocity and radius of curvature of the endeffector trajectory, has been suggested as a fundamental constraint of the central nervous system in the formation of rhythmic endpoint trajectories. However, studies on the 2/3 power law have largely been confined to planar drawing patterns of relatively small size. With the hypothesis that this strategy overlooks nonlinear effects that are constitutive in movement generation, the present experiments tested the validity of the power law in elliptical patterns which were not confined to a planar surface and which were performed by the unconstrained 7-DOF arm with significant variations in pattern size and workspace orientation. Data were recorded from five human subjects where the seven joint angles and the endpoint trajectories were analyzed. Additionally, an anthropomorphic 7-DOF robot arm served as a "control subject" whose endpoint trajectories were generated on the basis of the human joint angle data, modeled as simple harmonic oscillations. Analyses of the endpoint trajectories demonstrate that the power law is systematically violated with increasing pattern size, in both exponent and the goodness of fit. The origins of these violations can be explained analytically based on smooth rhythmic trajectory formation and the kinematic structure of the human arm. We conclude that in unconstrained rhythmic movements, the power law seems to be a by-product of a movement system that favors smooth trajectories, and that it is unlikely to serve as a primary movement generating principle. Our data rather suggests that subjects employed smooth oscillatory pattern generators in joint space to realize the required movement patterns.

am

link (url) [BibTex]

link (url) [BibTex]